Add the fs_context_operations method .reconfigure that performs
remount validation as previously done by the super_operations
.remount_fs method.
An attempt has also been made to update the comment about options
handling problems with mount(8) to reflect the current situation.
Signed-off-by: Ian Kent <raven@xxxxxxxxxx>
---
fs/xfs/xfs_super.c | 171 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 171 insertions(+)
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 0ec0142b94e1..7326b21b32d1 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1721,6 +1721,176 @@ xfs_validate_params(
return 0;
}
+STATIC int
+xfs_reconfigure(
+ struct fs_context *fc)
+{
+ struct xfs_fs_context *ctx = fc->fs_private;
+ struct xfs_mount *mp = XFS_M(fc->root->d_sb);
+ struct xfs_mount *new_mp = fc->s_fs_info;
+ xfs_sb_t *sbp = &mp->m_sb;
+ int flags = fc->sb_flags;
+ int error;
+
+ error = xfs_validate_params(new_mp, ctx, fc->purpose);
+ if (error)
+ return error;
+
+ /*
+ * There have been problems in the past with options
+ * passed from mount(8).
+ *
+ * The problem being that options passed by mount(8) in
+ * the case where only the the mount point path is given
+ * would consist of the existing fstab options with the
+ * options from mtab for the current mount merged in and
+ * the options given on the command line last. But the
+ * result couldn't be relied upon to accurately reflect the
+ * current mount options so that rejecting options that
+ * can't be changed on reconfigure could erronously cause
+ * mount failure.
+ *
+ * The mount-api uses a legacy mount options handler
+ * in the VFS to accomodate mount(8) so these options
+ * will continue to be passed. Even if mount(8) is
+ * updated to use fsopen()/fsconfig()/fsmount() it's
+ * likely to continue to set the existing options so
+ * options problems with reconfigure could continue.
+ *
+ * For the longest time mtab locking was a problem and
+ * this could have been one possible cause. It's also
+ * possible there could have been options order problems.
+ *
+ * That has changed now as mtab is a link to the proc
+ * file system mount table so mtab options should be
+ * always accurate.
+ *
+ * Consulting the util-linux maintainer (Karel Zak) he
+ * is confident that, in this case, the options passed
+ * by mount(8) will be those of the current mount and
+ * the options order should be a correct merge of fstab
+ * and mtab options, and new options given on the command
+ * line.
+ *
+ * So, in theory, it should be possible to compare incoming
+ * options and return an error for options that differ from
+ * the current mount and can't be changed on reconfigure to
+ * prevent users from believing they might have changed mount
+ * options using remount which can't be changed.
+ *
+ * But for now continue to return success for every reconfigure
+ * request, and silently ignore all options that can't actually
+ * be changed.
+ */
+
+ /* inode32 -> inode64 */
+ if ((mp->m_flags & XFS_MOUNT_SMALL_INUMS) &&
+ !(new_mp->m_flags & XFS_MOUNT_SMALL_INUMS)) {
+ mp->m_flags &= ~XFS_MOUNT_SMALL_INUMS;
+ mp->m_maxagi = xfs_set_inode_alloc(mp, sbp->sb_agcount);
+ }
+
+ /* inode64 -> inode32 */
+ if (!(mp->m_flags & XFS_MOUNT_SMALL_INUMS) &&
+ (new_mp->m_flags & XFS_MOUNT_SMALL_INUMS)) {
+ mp->m_flags |= XFS_MOUNT_SMALL_INUMS;
+ mp->m_maxagi = xfs_set_inode_alloc(mp, sbp->sb_agcount);
+ }
+
+ /* ro -> rw */
+ if ((mp->m_flags & XFS_MOUNT_RDONLY) && !(flags & SB_RDONLY)) {
+ if (mp->m_flags & XFS_MOUNT_NORECOVERY) {
+ xfs_warn(mp,
+ "ro->rw transition prohibited on norecovery mount");
+ return -EINVAL;
+ }
+
+ if (XFS_SB_VERSION_NUM(sbp) == XFS_SB_VERSION_5 &&
+ xfs_sb_has_ro_compat_feature(sbp,
+ XFS_SB_FEAT_RO_COMPAT_UNKNOWN)) {
+ xfs_warn(mp,
+"ro->rw transition prohibited on unknown (0x%x) ro-compat filesystem",
+ (sbp->sb_features_ro_compat &
+ XFS_SB_FEAT_RO_COMPAT_UNKNOWN));
+ return -EINVAL;
+ }
+
+ mp->m_flags &= ~XFS_MOUNT_RDONLY;
+
+ /*
+ * If this is the first remount to writeable state we
+ * might have some superblock changes to update.
+ */
+ if (mp->m_update_sb) {
+ error = xfs_sync_sb(mp, false);
+ if (error) {
+ xfs_warn(mp, "failed to write sb changes");
+ return error;
+ }
+ mp->m_update_sb = false;
+ }
+
+ /*
+ * Fill out the reserve pool if it is empty. Use the stashed
+ * value if it is non-zero, otherwise go with the default.
+ */
+ xfs_restore_resvblks(mp);
+ xfs_log_work_queue(mp);
+
+ /* Recover any CoW blocks that never got remapped. */
+ error = xfs_reflink_recover_cow(mp);
+ if (error) {
+ xfs_err(mp,
+ "Error %d recovering leftover CoW allocations.", error);
+ xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
+ return error;
+ }
+ xfs_start_block_reaping(mp);
+
+ /* Create the per-AG metadata reservation pool .*/
+ error = xfs_fs_reserve_ag_blocks(mp);
+ if (error && error != -ENOSPC)
+ return error;
+ }
+
+ /* rw -> ro */
+ if (!(mp->m_flags & XFS_MOUNT_RDONLY) && (flags & SB_RDONLY)) {
+ /*
+ * Cancel background eofb scanning so it cannot race with the
+ * final log force+buftarg wait and deadlock the remount.
+ */
+ xfs_stop_block_reaping(mp);
+
+ /* Get rid of any leftover CoW reservations... */
+ error = xfs_icache_free_cowblocks(mp, NULL);
+ if (error) {
+ xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
+ return error;
+ }
+
+ /* Free the per-AG metadata reservation pool. */
+ error = xfs_fs_unreserve_ag_blocks(mp);
+ if (error) {
+ xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
+ return error;
+ }
+
+ /*
+ * Before we sync the metadata, we need to free up the reserve
+ * block pool so that the used block count in the superblock on
+ * disk is correct at the end of the remount. Stash the current
+ * reserve pool size so that if we get remounted rw, we can
+ * return it to the same size.
+ */
+ xfs_save_resvblks(mp);
+
+ xfs_quiesce_attr(mp);
+ mp->m_flags |= XFS_MOUNT_RDONLY;
+ }
+
+ return 0;
+}
+
/*
* Second stage of a freeze. The data is already frozen so we only
* need to take care of the metadata. Once that's done sync the superblock
@@ -2246,6 +2416,7 @@ static const struct super_operations xfs_super_operations = {
static const struct fs_context_operations xfs_context_ops = {
.parse_param = xfs_parse_param,
.get_tree = xfs_get_tree,
+ .reconfigure = xfs_reconfigure,
};
static struct file_system_type xfs_fs_type = {
